Now defeated, Iraq's most feared jihadists await their fate

Their names spread terror across the Islamic State group's cross-border "caliphate", but senior jihadists now languish in Iraqi prisons, subjects of mockery for the populace they ruled.

Once boasting nicknames like the Black Box and the Butcher of Mosul, the defeated IS commanders now draw vitriol on social media while news outlets have published selfies taken by Iraqi soldiers of them being captured or marched handcuffed in prison uniforms.

Following the jihadist group's ouster from second city Mosul last July, Iraqi forces went on the hunt for IS fighters who had fled the battlefield.

Researchers estimate they have since put behind bars some 20,000 suspected members of the group.

The search involved digging through the rubble of war-torn Mosul and hunting through the tunnels and hideouts the jihadists had created during their three-year reign.

It was in Mosul's Old City, near the al-Nuri mosque where the self-proclaimed "caliph" Abu Bakr al-Baghdadi made his only public appearance, that the elite Counter-Terrorism Service found the senior commander nicknamed the "Black Box of IS" -- a moniker that came from his lynchpin role in the organisation.

Nizam Eddin al-Rifai had sent gunmen and suicide bombers in a desperate bid to repel government troops, said Sabah al-Noman, spokesman for elite units that spearheaded the Mosul offensive.

But in the end he had no choice but to surrender. Cornered by government soldiers, he left his underground hideout bare-chested, his unkempt beard matching his white hair.

Time was finally up for the notoriously hardline head judge of the "caliphate" which at its height ruled over roughly seven million people in Iraq and Syria.

The 60-year-old Mosulite is still under interrogation, Noman said, adding that he could still give up valuable information about IS.

Rifai's position made him the group's third in command, according to security sources speaking on condition of anonymity.

He also had the symbolically important role of "teaching theology to Abu Bakr al-Baghdadi," the jihadists' self-proclaimed "caliph", they said.